High voltage disconnect switches and circuit interrupters are used for a variety of purposes, such as interrupting line, loop, and load currents and switching reactors, capacitors and other circuit devices. Different types of switches are designed to meet different needs. Examples of high voltage circuit interrupters are described in commonly-owned U.S. Pat. Nos. 7,115,828; 7,078,643; 6,583,978; 6,483,679; 6,316,742 and 6,236,010. Disconnect switches and circuit interrupters are designed to switch currents well below fault current levels and operate relatively frequently, such as daily. Circuit breakers, which are used to interrupt much higher fault currents, are typically more expensive and designed to operate much less frequently. The purpose of the present invention is a reliable and cost effective accessory to a high voltage disconnect switch to interrupt line charging, loop splitting and load currents eliminating the need to operate a fault clearing device such as a circuit breaker.
Prior approaches to disconnect switches for these applications include external whips and arcing horns, vacuum bottles, external whips and vacuum bottle in combinations, and puffer type dielectric gas (e.g., SF6) interrupters. Whips and arcing horns, which use exposed air arcing, are suitable only for line charging with line currents limited current to approximately 15 Amps. For vacuum bottles, single bottles are limited to distribution voltages. Multiple bottles in series are required for higher voltages which increases cost and decreases reliability. Because of the increased cost and complex of multi-bottle configurations, linkages are used in order to share a single unit for two and three way switches. In whip and single vacuum bottle combinations, the vacuum bottle interrupts loop switching and the whip interrupts line charging current. Vacuum bottle voltage rating is limited by an optimum contact gap distance which limits the voltage rating to distribution class interrupters. Multiple vacuum bottles in series are required to reach transmission voltage ratings increasing the complexity and cost. Whips and arcing horns are limited in interrupting current since the arcing takes place in air. This can also be a hazard to operating personnel. In general, these configurations are not well suited for interrupting line charging currents and are relatively expensive.
Puffer type dielectric gas interrupters have high operating forces and are the most expensive solution. They are physically larger, heavier, and are not readily adapted to pole mounted transmission switches. They typically have the highest interrupter ratings for interrupter switches.
Spinning arc dielectric gas interrupters have been used as fault current interrupters. In conventional arc spinning dielectric gas interrupters, the magnetic field is generated by directing the current going through the interrupter through field coils to generate the magnetic field to spin the arc. The field coils are typically located in the center of the contacts with opposite poles aligned across the arc gap. In addition, the strength of the magnetic field varies with the current that passes though the interrupter, which generates the magnetic field to spin the arc. These fault current interrupters are typically complex, designed to interrupt high fault current, and are not suited to interrupting lower-level currents, such as line, loop, and load currents because the magnetic flux is a function of the current passing through the coil located in the interrupter.
There is, therefore, a continuing need for a circuit interrupter in which the magnetic flux is at least in part not a function of the current passing through the interrupter to render the interrupter suitable for switching line, loop, and load currents on high voltage transmission lines while eliminating the need to operate a fault clearing device, such as a circuit breaker, to interrupt these types of currents.